This invention relates to an improved erythrocyte preservation method and composition. More particularly, this invention relates to such improvements in the storage of whole blood and of packed blood cells suitable for transfusion.
The biochemical processes that occur during blood preservation all contribute to the diminished post transfusion erythrocyte survival ability statistically correlated with the duration of storage time. Maintenance of in vivo survival ability of red cells is closely correlated to glucose metabolism and specifically associated with the maintenance of higher levels of cellular ATP (Adenosine Tri Phosphate). It has been postulated that ATP levels preserve membrane integrity by maintaining proper ionic transport gradients across the red cell membrane, adequate lipid turnover rate, hemoglobin in a functional state and normal equilibrium of oxidized and reduced glutathione, along with synthesis of adequate amount of NAD.sup.+ and NADP.sup.+. (Nicotinamide Adenine Dinucleotide and its Phosphate.)
Several studies are under way incorporating various chemical additives along with CPD (citrate-phosphate-dextrose) anticoagulant to stimulate glycolysis, yielding a net increase in ATP levels. One of these chemical additives currently being studied is adenine. The incorporation of adenine along with CPD anticoagulant into stored blood appears to increase ADP (Adenosine DiPhosphate) levels, thereby driving the glycolysis equilibrium towards the synthesis of ATP. However, adenine has an adverse effect on the maintenance of the levels of another important organic phosphate, namely 2,3DPG ( 2,3 diphosphoglycerate). Recent concern over the levels of ATP and 2,3DPG has become a controversial subject. Because the main objective of transfusing patients is to provide oxygen delivery to the tissues, the blood oxygen affinity, directly determined by 2,3DPG levels, may be of critical importance. Therefore, in providing patients with suitable blood for transfusion one must now evaluate red cell viability not only in terms of ATP levels but also 2,3DPG levels to insure a nearly normal oxygen affinity for adequate hemoglobin-oxygen transport function, the ultimate goal of red cell transfusion. The dependence of normal hemoglobin function on 2,3DPG levels in the red cell has been well documented. As a result, current research is also geared towards incorporation of chemicals into the CPD storage solution to increase 2,3DPG levels.
Some of these chemicals under current investigation include inosine, methylene blue, pyruvate, dihydroxyacetone and ascorbic acid, along with various combinations of these additives; see, for example, U.S. Pat. No. 3,795,581.
Various clinical observations during such conditions as congestive heart failure, right to left cardiac shunts and hypoxemia due to pulmonary disease support the assumption that hemoglobin oxygen affinity is an important factor in determining oxygen delivery in vivo. The transfused red cell, totally depleted of 2,3DPG, can regain half the normal level within about twenty-four hours but this reconditioning may not be rapid enough to be effective in a severely ill patient. Furthermore, it is not known whether the rate of resynthesis of 2,3DPG in the donor cells given to critically ill patients is comparable to that observed in normal recipients. There seems to be a direct correlation between the ability to compensate for low 2,3DPG levels (generally implying a strong hemoglobin-oxygen affinity) and the severity of the illness of the patient, as has been reported by Dennis, et al in Surgery 77 (6):741-747 (June, 1975).
Blood with nearly normal hemoglobin-oxygen affinity is thus preferable for use in massive transfusions, particularly in infants, older patients and patients with complicating cardiovascular and pulmonary disease.
The physiological effects of high oxygen-affinity 2,3DPG depleted red cells on the myocardial, cerebral, hepatic and renal functions have not yet been fully evaluated, but patients requiring massive transfusions seem to be most susceptible to the adverse effects due to very low levels of 2,3DPG; see Beutler, et al, Vox Sang. 20:403-13 (1970).
Although numerous investigations indicate that red cell levels of ATP and 2,3DPG can be better maintained when the two chief preservative solutions ACD (acid citrate dextrose) and CPD (citrate-phosphate-dextrose) are supplemented with adenine, inosine or both during storage at 4.degree. C, this must be approached with some caution. As has been reported by Bunn, et al in New England J. Med 282:1414-21 (1970), a patient receiving three or four units of thus-supplemented blood may develop hyperuremia, which would persist for approximately twenty-four hours. As reported by Valeri in J. Med. (Basel) 5(5):278-291 (1974), a further cause for concern is the possible renal toxicity of 2,8-dioxyadenine, a metabolite of adenine. No matter which chemical is used with an ACD or CPD preservative solution, it appears that only a combination of various chemical additives will maintain 2,3DPG levels past the third week of storage. Such combinations of chemical additives present definite complications in terms of renal toxicity.